摘要：The woven textile sandwich composite（WTSC） is a promising lightweight *** bending,two competing core shearing failure modes reduce the strength;deflection induced by the core shearing deformation reduces the flexural *** replace a solid composite laminate,the span of WTSC panel must be greater than a critical value,which was deduced on the condition that the load capacity and flexural rigidity of the WTSC panel are equal to those of the composite *** WTSC panels were tested in bending,so that the failure modes were observed,and the critical spans were *** the alternative design method,the WTSC based wind deflector with reduced weight has been fabricated and mounted on the CRH（China Railway High-speed）.

摘要：The development of a high-performance cemented carbide drill bit is of great significance to the reduction of rock drilling-cost. The non-smooth features of a biological surface provide an insight into how they can obtain low friction and good wear resistance with evolving surface morphology. By analyzing the mechanism of the surface of a dung beetle for reducing soil wear and adherence, we design a cemented carbide drill bit with a bionic surface, which is expected to have superior anti-wearing and anti-sticking properties for drilling the soft coal seam. Inspired from the characteristics of the head and pronotum surface of the dung beetle, optimized non-smooth surface of the drill bit was constructed. The working performance of this innovative drill was experimentally tested. With comparative experiments under the identical drilling conditions, the wear rates, drilling times of conventional drills and bionic drills were measured. Compared with the conventional counterpart, the drill designed exhibits better performance in reducing wear and sticking drilling-breaks, therefore achieving higher levels of efficiency. The diameter of the dome and pit on the bit surface is in the range of 0.8–1.2 mm, and the bionic drill bits could get better performance with preferable drilling speeds and wear rates.

摘要：In wind tunnel tests,long cantilever stings are usually used to support aerodynamic ***,this kind of sting support system is prone to vibration problems due to its low damping,which limits the test envelope and affects the data *** is shown in many studies that the sting vibration can be effectively reduced by using active sting dampers based on piezoelectric *** paper attempts to review the research progress of piezoelectric vibration control in wind tunnel tests,covering the design of active sting dampers,control methods and wind tunnel *** of all,different design schemes of active sting dampers are briefly introduced,along with the vibration damping ***,a comprehensive review of the control methods for active sting dampers is presented,ranging from classic control methods,like PID control algorithm,to various intelligent control ***,the applications of active sting dampers and controllers in different wind tunnels are summarized to evaluate their vibration damping ***,the remaining problems that need to be solved in the future development of piezoelectric vibration control in wind tunnel tests are discussed.

摘要：具有随机孔隙的多孔泡沫在声音管理应用中得到越来越多的利用,其吸声系数通常作为性能评估和设计优化的关键声学参数.根据不同的加工方法,泡沫中的孔隙可以是全开或半开的,并且通常表现为分形分布特征.为了便于工程应用,有必要对这些泡沫的吸声系数进行分析预测.然而,分析预测泡沫的吸声系数是一个挑战.因此,本研究提出了半开孔和全开孔的简化代表结构来微观分析泡沫内部的流动特性,并应用分形理论来描述随机分布的孔隙.引入一个叫“开孔度”的参数来表征孔隙的开放程度,可以解析地获得代表结构的粘性和热特征长度.随后,在经典吸声系数Johnson-Champoux-Allard模型的基础上,建立了一种将代表结构与分形理论统一起来的解析模型,从而可以将吸声系数作为具有全开/半开孔泡沫的关键形态参数的函数进行预测.与已有的实验测量和数值模拟结果相比,本文提出的分析模型可以较好地预测了半开孔和全开孔泡沫的关键流动特性和吸声系数.在0到4500 Hz的频率范围内,半开孔泡沫相对于具有相同孔隙率的全开孔泡沫可以更好地衰减声波.在孔隙率为0.95的条件下,半开孔泡沫的总体吸声系数分别提高了21.2%、57.7%和75.8%,此时开孔度由0.75到0.50降低了0.25.

摘要：针对脉宽调制型Buck变换器的内外干扰和滑模控制的抖振等问题,本文提出了一种基于降阶扩张状态观测器和无抖振滑模的新型控制策略.首先,建立新型的跟踪误差状态空间模型,将匹配和不匹配干扰定义为统一的匹配干扰;然后,设计降阶扩张状态观测器提高跟踪误差微分和系统干扰的估计速度,并抵消负载和输入端的电压变化、系统参数不确定性对控制系统的影响;其次,利用跟踪误差微分的估计值设计滑模控制器抑制干扰估计误差,使得切换项近似为零,实现滑模技术的无抖振控制,提高Buck变换器系统电压跟踪的快速性和准确性.利用李雅普诺夫稳定判据从理论上证明了所提控制器的闭环稳定性.最后,仿真结果表明所提方法通过抑制抖振和内外干扰有效改善Buck变换器的鲁棒性和动态性能.

摘要：A piezoelectric pump with flexible valve has been developed to pump high viscosity cooling liquid in the nanosats thermal control system. The structure of the flexible valve is designed according to the characteristics of the human aortic shape with the aim to simulate the bionic pumping function of the human heart. Dynamic stress-strain features of the flexible valve are analyzed by the finite element method,and the results show that the proposed flexible valve is suitable and functional for the piezoelectric pump. Then the cylinder and diffuser/nozzle piezoelectric pumps based on flexible valves have been developed and fabricated. Experimental results of the output performance indicate that the maximum flow rate of the cylinder piezoelectric pump with flexible valve is 15.38 mL/min,170.77% higher than the diffuser/nozzle piezoelectric pump with flexible valve. The ability of the cylinder piezoelectric pump with flexible valve for transmitting high viscosity liquid has been validated. The piezoelectric pump with flexible valve has potential applications in the nanosats thermal control system.